Woo hoo, I like the look of those o-rings. Have you tried to get them at a local True Value?

The teflon tape Cayugad suggested and the longer Winchester W209 primers will likely improve things.

The box of 777 primers I have on hand are the same exact length as the Win209's. I am not sure why some say the Win 777 primers are shorter?

Good luck finding the metric o-rings in any local stores. Buy a few packs and it will cost you around $12 or $13 and your set for years of shooting. Heck, I have gave more away then I have used!!

I used to work for John Deere...

If you go to the parts counter and ask to see the o'ring
box they will bring it out and you can find just about any
size you need...